In Patent Literature 1, there is disclosed an indoor unit for an air-conditioning apparatus. The indoor unit includes a heat exchange chamber and a machine chamber. In the heat exchange chamber, a heat exchanger through which flammable refrigerant flows is arranged. In a lower part of the heat exchange unit, a drain pan configured to receive and drain condensate water generated in the heat exchanger is arranged. The drain pan extends from the lower part of the heat exchange chamber to a lower part of the machine chamber. A sensor configured to detect the flammable refrigerant is arranged in a vicinity of the drain pan in the lower part of the machine chamber. When the flammable refrigerant leaks from the heat exchanger, the flammable refrigerant is guided to the lower part of the machine chamber along the drain pan to be detected by the sensor.
In Patent Literature 2, there is disclosed a gas sensor. The gas sensor includes a gas detection device and a frame member configured to accommodate the gas detection device therein. A large number of air holes are formed in the frame member to cause indoor air to flow toward the gas detection device.